<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>

    <ul id="uls">
        <li></li>
        <li></li>
        <li></li>
        <li></li>
    </ul>

</body>
<script>
    var ul = document.getElementById('uls');

    ul.addEventListener('click', function(e) {
        e.target.style.backgroundColor = 'red';
    })
</script>

</html>